Disconnecting of well pipe or tubing joints



June 17, 1958 F. ALEXANDER DISCONNECTING 0F WELL PIPE OR TUBING JOINTS Filed Jan. 16, 1956 Z 8 a a w w w 2 w a Z M R m E W w m N A I X E a I D R United DISCDNNECTING F WELL PIPE OR TUBING JQINTS This invention relates to improved methods and apparatus for disconnecting a selected joint of a string of pipe or tubing which is stuck within a well.

In the drilling of a Well, it happens fairly frequently that a string of pipe, usually the drill pipe, becomes stuck at a location deep within the well. For instance, this may happen by reason of a cave-in of the earth formation against the pipe, or as a result of various other types of conditions that may arise.

The general object of the present invention is to provide improved methods and apparatus for disconnecting a selected joint of such a stuck string, at a point just above the stuck location, so that an upper free portion of the string may be detached from the stuck portion and then withdrawn separately from the well. Preferably, the apparatus is adapted, on a single run into the well, to first locate the highest point at which the string is stuck, then to find the nearest joint above that point, and finally to break that joint.

The disconnecting of a joint in accordance with the present invention involves a unique combination of two factors which function together to break the joint. More specifically, I apply to the joint a force in a direction tending to break the joint, and in combination with that force I locally change the temperature of the joint to an extent sufiicient to initiate unthreading of the joint under the applied force. The force which is applied to the string in combination with the change in temperature may be either a lifting force or an unscrewing torque, but preferably includes a combination of both of these types of force.

The present invention is in certain respects particularly concerned with a process in which the temperature change is effected by cooling of a portion of the joint, or by cooling one portion of the joint and heating another portion. My related copending application Serial No. 532,636, filed September 6, 1955, and entitled Method and Apparatus for Disconnecting Well Pipe Joints includes claims directed specifically to the novelty residing in the use of heat for the purpose, whether or not the heat is associated with a cooling effect.

The cooling eifect is attained by use of a cooling unit which may be lowered into a well to a location adjacent the joint which is to be broken, and which can then drastically lower the temperature of one section of the joint to contract it so that the applied force will be able to initiate the unthreading of the joint. Preferably, the cooling unit is positioned adjacent and cools mainly the externally threaded pin section of the joint, to contract that section relative to and away from the engaged internally threaded box section. If a further effect is necessary, a heater may be lowered with the cooling unit,

to be received opposite and to heat primarily the box section of the joint, to thus expand the box section and encourage its separation from the pin section. Also, a conventional free point indicator and a joint finder may be lowered with the cooling unit and heater for atent G ice properly locating these units opposite the desired joint.

The above and other features and objects of the present invention will be better understood from the following detailed description of the typical embodiments represented in the accompanying drawing in Which:

Fig. 1 is a partially schematic representation of a well containing a stuck drill string, together with the apparatus which is utilized for breaking one of the joints of the string directly above the stuck point;

Fig. 2 is an enlarged fragmentary vertical section through a portion of the Fig. 1 apparatus, and

Fig. 3 is a fragmentary sectional view similar to Fig. 2, but showing a variational form of the invention.

Referring first to Fig. l, I have shown at 10 a well bore, containing a rotary drilling string 12 or other pipe string which has become stuck in the well. The lower portion of the drill string 12 may be considered as being stuck up to a point 13, typically by caving in of the lower portion of the well in a manner tightly packing the earth about the drill string. Above the point 13, the string 12 is free, and it is therefore desired to break the nearest threaded joint 14 above point 13, so that the portion of the string above joint 14 may be recovered from the well.

As seen best in Fig. 2, each of the joints 14 of the drill string 12 includes the usual threaded pin and box sections 15 and 16, which are connected together by right hand rotation of the upper pin section, and which are then effective to transmit rotary motion from the pin section to the box section, so that rotation of the upper end of the drill string in a right hand direction turns the entire string during a drilling operation. The threads 17 interconnecting sections 15 and 16 are normally of a tapered configuration, as shown, and are made up sufiiciently tightly to require a considerable unwinding torque in order to break the joint.

The movements of the drill string are controlled by the usual equipment 13 at the surface of the earth, including a power driven rotary table 19 adapted to receive slips 20 for suspending the weight of string 12. The rig 18 includes also a derrick 21, having a travelling block 22 from which string 12 may be supported by a suspension element 23, block 22 being movable upwardly by winding of its cable 24 on the usual power driven elevating drum 25.

For conditioning a particular joint 14 to be broken by forces exerted by the rotary table and travelling block, I lower into the well on a suspending cable 26 a cooling or refrigerating unit 27, which acts to internally cool the upper pin section 15 of the lowermost free joint 14, to a temperature such that vertical and rotary forces exerted against the upper end of the pipe by the rotary table and travelling block will be effective to break the desired joint, while leaving the other joints of the string intact. This cooling unit 27 may include a vertically elongated tubular preferably metal and fluid tight outer housing 28, containing a quantity of material 29 which is in a highly compressed state, and which is adapted when freed from housing 2? to very rapidly expand to a gaseous state, and to absorb a large quantity of heat from joint section 15 as a result of its vaporization. The material 29 may be a normally gaseous material such as carbon dioxide or oxygen, which is in a liquid state before being freed from housing 28. The housing is of course rigid and sufficiently strong to withstand the pressure of the refrigerating substance 29.

The charge of refrigerating material 29 may be contained within an upper compartment in the housing, above a partition 51. The discharge of the refrigerant 29 may be controlled by a valve 52, through which the refrigerant may pass to the underside of partition 51, for discharge laterally from the housing through a line 52a and an opening 53 in the side of the lower portion of housing 28.

After leaving opening 53, the refrigerating fluid rapidly expands and rises in gaseous form through the well, so that the evaporation and expansion of the fluid cause a rapid cooling and thus contraction of the externally threaded pin 15. Valve 52 may be actuable from closed to open positions by means of an electrically energized solenoid 54 to which current is supplied from a power source 55 under the control of a switch 56 at the surface ofthe earth.

Cable 26 also preferably suspends, desirably at a location above cooling unit 27, a conventional free point indicator or stuck'point indicator 34, which electrically controls an associated indicating unit 135 at the surface of the earth, in a manner such that the indicator locates the uppermost point 13 at which string 12 is' stuck. This'free point indicator may be of any of the well known types now in use, and need not be described in detail for present purposes. To describe one form of free point indicator 34 very briefly, this device may include two tubular vertically extending elements or sections 35 which interfit telescopically at 36 in a manner allowing relative vertical telescopic movement of the two sections. A set of upper bowed springs 37 carried by the upper section 35' of device 34 acts to frictionally hold that section in a particular set position Within drill string 12, while a second and lower set of springs 38 acts to correspondingly frictionally hold the lower section35 in a desired set position. When unit 34 is lowered into the drill string to a particular location, and travelling block 22 is then actuated to exert a vertical force against the string, the resulting slight relative movement of the two sections 35 of unit 34 acts through a strain gauge or other responsive member contained within the device to produce an electrical response which is indicated to an operator at the surface of the earth on the indicating unit 135. If this same type of operation is performed with free point indicator 34 positioned in string 12 at a location beneath the stuck point or free point 13, the engaged portion of the string of course will not be elongated or extended even slightly when travelling block 22 is actuated to exert an upward force on the string, so that the indicating unit 135 will apprise an operator of the fact that the unit 34 is within a stuck portion of the pipe. By thus taking a series of readings from stuck point indicator 34, it is possible to very precisely locate the uppermost point 13 at which the drill pipe is stuck.

After the point 13 has thus been determined, it is desirable to elevate cooling unit 27 upwardly to its Fig. 1

position within pin section of the next upper joint 14, in order that that joint may be broken. joint 14 for such positioning of cooling unit 27, I sus pend on cable 26, in addition to unit 27 and free point indicator 34 (and preferably vertically therebetween and substantially directly adjacent unit 27) a conventional instrument of the type referred to as an electrical joint finder, designated 39 in the drawing. As in the case of instrument 34, it is unnecessary for present purposes to describe specifically the construction of joint finder 39, other than to say that it includes a bodyor housing 40 movably carrying a laterally projecting and typically spring pressed, finger or element 41, which is deflected relative to body 40 by engagement with the reduced dimension portion 42 of the drill string at each joint 14, and which electrically controls an indicator 43 at the surface of the earth to tell when joint finder 39 is positioned within one of the joints 14. indicator 43, joint finder 39 and a power source 139 may be connected into a series electrical circuit (see Fig. 1) one side of which is typically grounded; and indicator 1.35, unit 34 and a power source 239 may be connected into a similar circuit.

As an example of one ofthe various types of conventional stuck point indicators which have been utilized commercially in the past, reference is made to U. '8.

To locate the 4 Patents 2,530,308 and 2,530,309. Similarly, as an example of the type of device which could be utilized as the joint finder in the present apparatus, reference is made to U. S. Patent 2,322,343.

In performing a joint breaking operation in accordance with the present method, a first step may be to lower the instruments 27, 39 and 34 into the stuck drill pipe 12. The drill pipe elevating mechanism 22-25 may then be actuated, by driving drum 25, to exert an upward force on the upper end of drill string 12, this upward force or movement preferably being sufiicient to lift substantially all of the weight. of the drill string 01f of the joint 14. Slips 20 may then be inserted into the rotary table, so that the drill pipe is suspended from the rotary table in the described condition in which the weight of the pipe is relieved from joint 14. Rotary table 19 is then driven in a left hand direction with a force to apply a very substantial unscrewing torque to the upper pin section 15 of the joint 14 which is to be unscrewed. This torque is sufiiciently great to perform the desired function of assisting in breaking the joint 14, While at the sme time being insuificient totwist off or otherwise damage the pipe.

Cooling unit 27 is properly located the desired joint 14 by first utilizing free point indicator 35 to determine the exact location of the uppermost stuck point 13 following which cable 26 is pulled upwardly to azpointat which indicating unit 43 responsive to joint finder 39 indicates that instrument 39'is located directly within the nearest joint 14 above point 13. After this position has been located, cable 26 is raised through a predetermined measured distance corresponding to the efiective vertical spacing between unit 39 and unit 27, which raising of cable .26 is just suificient to very accurately locateunit 27 in its Figs. 1 and 2 position within the upper pin section of joint 14.-

With cooling unit 27 positioned as shown in Fig. 2 within pin section 15, and with the weight of string. 12 suspended and an unscrewing'torque applied by rotary table 19.215 previously discussed, switch 56 at the surface of the earth may be closed to energize solenoid 54an'd thus open valve 52;. This frees liquid oxygen or carbon dioxide or other compressed material 29 for rapid evaporation and expansion outwardly through aperture 53 and then upwardly between housing 28 and pin section 15, to rapidly cool pin section 15.' This'cooling causes contraction of the pin section, which contraction sufficiently loosens the joint to enable the torque and suspending forces exerted against the drill string to break the threaded joint. If the joint does not break when the temperature is thus lowered by unit 27, slips 20 may be removed from the rotary table 19, and drum 25 may be alternately driven several times in opposite rotary directions to alternately exert an upward force against. the drill string and then'allow the weight of the string to again 'rest on the joint 14. Preferably, during such repeated suspension and release of the drill string, an unscrewing'torque is exerted against the upper section ofserve to break even the most tightly made joint 14.-

After the threaded connection is broken, the instruments 27, 39 and 34 may be withdrawn upwardly from the well, and rotary table 19 may be driven to complete the unscrewing of the upper portion of the pipe from the lower stuck portion at joint 14, following which the upper-p01"- tion may be removed upwardly from the well, leaving the lower stuck portion in the well. Subsequent operations may of course be performed to free a portion or all of the stuck pipe, so that it too may be removed from the well. Y

It will of course be understood that various other types of cooling or refrigerating units could be substituted for that shown typically at 27 in the drawings. However, regardless of what type of cooling unit is employed, it must function to lower the temperature of pin section 15 under normal well conditions to a rather low temperature, preferably to a temperature at least as low as about 32 F., and for best results as low as about 0 F. Also, unit 27 should lower the temperature of the pin section at least aboutlOO F. lower than the ambient temperature, that is, the temperature of the adjacent formation prior to cooling. The cooling effect of unit 27 is desirably applied over a somewhat extended period of time, rather than merely instantaneously, preferably over a period of at least about one minute, and desirably between one and ten minutes. If the joint is still stuck after being cooled for a substantial period of time, say ten minutes, and if some of the coolant 29 still remains in housing 28, then valve 52 may be alternately opened and closed for a few minutes at a time, to cause the joint to alternately contract and expand, and thus increase the possibility of breaking the joint.

Fig. 3 represents fragmentarily a variational form of the invention, which may be substantially identical with that shown in Figs. 1 and 2 except as for the provision of a heater element 57 on line 26a in addition to the cooling unit 270 and the joint finder and the free point indicator previously described (the joint finder and free point indicator are not shown in Fig. 3). Heater element 57 typically includes a vertically elongated tubular preferably metal and fluid tight outer housing 58, containing a suitably insulated electrical heater element or coil 59, adapted to be energized by current from a suitable electrical power source 60 at the surface of the earth. One side of the power soure 6!} may be connected to heater element 59 through a ground connection 61, while the other side of power source 69 may be connected to the heater element through a switch 62 and a lead 63 extending downwardly within the well. Heater 57 is preferably suspended on line 26a at a location beneath cooling unit 27a, and is so positioned as to be received directly opposite the box section 16a of joint 14a, just slightly below the lowermost end of pin section 15a of the joint. Vertically between cooling unit 27a and heating unit 57, line 26a may carry a circular heat insulating part 64, formed of a material such as asbestos which conducts heat much less readily than the metal of the joint 14a, so that heater 57 functions to heat and expand mainly the box section 16a, while cooling unit 27a functions mainly to cool and contract pin section 15a, to cause the threads of the two sections to loosen and allow breaking of the joint.

In using the apparatus of Fig. 3, the cooling unit 27a and heater 57 are first accurately located in the illustrated Fig. 3 positions by means of the connected free point indicator and joint finder, in the manner previously discussed in connection with Figs. 1 and 3. Cooling unit 27a may then be actuated to a cooling condition by closure of switch 56 of Fig. 1, and heater 57 may be energized by closure of switch 62, to simultaneously heat section 16a and cool section 15a. The cooling and heating eifects may be continued until the previously applied torque and lifting forces exerted against pin section 15a act to break the threaded joint. Preferably, cooling unit 27a actsto cool section 15a to a temperature as low as 32 F. and for best results 0 F., and at least about 100 F. below the ambient temperature at the location of the joint in the well. Also, heater 57 should act to heat section 16a to a temperature at least about 150 F. above the ambient temperature. However, the temperature rise caused by heater 57 should not be great enough to destroy the temper or effect the hardness of the metal of box section 1611, and for this purpose the heater should not elevate the joint section temperature higher than about 950 F. The heating and cooling units should function to set up a temperature difierential between joint sections 15 and 16 of at least about 250 F. The heating and cooling effects should both be continued over a somewhat extended period of time, preferably for at least about one minute, and desirably between 1 and 10 minutes. Also, it is contemplated that in some instances, it may be desirable to initiate the heating etfect, by energizing heater 57, prior to the actuation of cooling unit 27a to initiate the cooling effect, with both the heater and cooler then being continued in operation after the latter is finally started; or it may be desirable to first start the cooler, and then subsequently the heater 57. In other instances, both the heating and cooling efiects will be simultaneously started and then stopped simultaneously. The extent to which the parts are heated and cooled may of course be predetermined by controlling the energization of the heater and by predetermining the amount of coolant in the cooling unit, knowing the zone temperature from prior temperature readings, or perhaps by actually taking temperature readings during the use of this apparatus.

While the invention has been described typically as applied to drill pipe, it will be apparent that the invention is also applicable to various other types of pipe, tubing, and casing which may be utilized in a well, and consequently the use of the word well pipe in the claims will be understood to include all of these types of tubing, etc, in which it may be desirable to disconnect a joint deep within a well.

I claim:

1. The method of breaking a predetermined threaded pin and box sections joint deep within a well between stands of a string of pipe stuck in the well, said pipe string having numerous other threaded joints above said predetermined joint; said method including lowering a cooling unit downwardly within said string and past said other joints to the location of said predetermined joint, applying force to the upper end of said string above said other joints in a direction tending to break the joint, and then actuating said cooling unit to locally cool the pin section of said predetermined joint below the temperature of its box section from the inside thereof to a temperature well below the ambient temperature at said joint to initiate unscrewing of that joint by said force as a result of the contraction caused by said cooling.

2. The method as recited in claim 1, in which said force includes a torque tending to unscrew the joint.

3. The method as recited in claim 1, in which said force includes a lifting force exerted against the string to relieve said joint of at least part of the weight of the string.

4. The method as recited in claim 1, in which said force includes a lifting force alternately applied and relieved to tend to vertically reciprocate the string.

5. The method of breaking a predetermined threaded pin and box sections joint deep within a well between stands of a string of pipe stuck in the well, said pipe string having numerous other threaded joints above said predetermined joint; said method including lowering a cooling unit downwardly within said string and past said other joints to the location of said predetermined joint, applying a lifting force to the upper end of the string above said other joints, applying a torque to said upper end of the string tending to unscrew all of said joints, and then actuating said cooling unit to locally cool the pin section of said predetermined joint below the temperature of its box section from the inside thereof to a temperature well below the ambient temperature at said joint to initiate unscrewing of that joint by said torque as a result of the contraction caused by said cooling.

6. The method as recited in claim 5, in which said litting force is alternately applied and relieved to tend to Vertically reciprocate the string.

7. The method as recited in claim 5, in which said cooling lowers the temperature of said pin section of the joint at least as low as about 32 F.

8. The method as recited in claim 5, in which said lifting force is alternately applied and relieved to tend to vertically reciprocate the string, said cooling being continued for at least about one minute, and acting to lower the temperature of said joint at least as low as about 32 F.

9. The method of breaking a threaded joint deep Within a Well between sections of a string of pipe stuck in the well, said joint including an externally threaded end or" one of said sections connected to an internally threaded end of the other section, said method comprising applying force to the string above said joint tending to break the joint, cooling said one section near said joint to a temperature below the ambient temperature at the joint, and heating said other section near said joint to a temperature sufiiciently above said ambient temperature to initiate unscrewing of the joint by the heat induced expansion of said other section and the contraction of said one section from said cooling.

10. The method as recited in claim 9, in which said heating and cooling develop a temperature differential of 8 at least about 250 F. between said interconnected ends of the two sections.

11. The method as recited in claim 9, in which said heating is commenced prior to said cooling and continues after the cooling commences. 7

' References Cited in the file of this patent UNITED STATES PATENTS Allen et a1 Apr. 24, 1934 2,033,560 Wells Mar. 10, 1936 2,257,3 9 Paulsen Dec. 23, 1941 2,305,261 Kinley n Dec. 15, 1942 2,322,343 Brandon June 22, 1943 2,433,55 Herzog Dec. 30, 1947 2,530,303 Martin Nov. 14, 1950 2,670,802 Acidey Mar. 2,1954 2,711,084 Bergan June 21, 1955 2,716,541 Helm Aug. 30, 1955 2,745,345 Sweetman May 15, 1956 

